The invention generally relates to pallets adapted for holding one or more substrates during processing. More particularly, in one embodiment, the invention is directed to substrate processing pallets adapted to maintain an aligned position during substrate processing and methods and machines employing such substrate processing pallets.
Conventional microelectronic and electro-optic device fabrication machines employ numerous processing steps including, for example, repetitive steps of depositing metal or dielectric films such as, silicon, gallium arsenide, and glass onto substrates. Such deposition typically takes place in an evacuated process chamber by way of any of a number of well know techniques, such as sputtering, evaporation and chemical vapor deposition (CVD).
Conventional substrate processing machines typically employ multiple chambers. By way of example, some conventional processing machines employ separate substrate storage, cleaning and deposition chambers. Typically, substrate processing machines employ complex mechanical mechanisms for transporting the substrates between the chambers. Conventional transport mechanisms can introduce substrate positioning errors. Additionally, during processing, the substrates and the various transport mechanisms and any substrate carrying pallets or pallets may be subjected to wide variations in temperature. Since the substrates, pallets/trays and transport mechanisms are typically formed from varying materials having varying thermal coefficients of expansion, exposure to temperature variations can introduce additional substrate positioning errors. Further, as a result of repetitive processing steps, these type of positioning errors can accumulate, causing even larger positioning errors. Some conventional processing machines employ such mechanisms as chain drives and tracking to reduce positioning error accumulation. However, such solutions tend to be expensive and complex.
One example of a conventional substrate processing machine employs cluster processing. Cluster processing machines provide a plurality of process chambers that are clustered around a central platform. A transport mechanism or robot moves the substrates between the various process chambers. Typically, each process chamber performs a single task and can be operated independently from the other process chambers. By way of example, individual process chambers may clean a substrate before processing, etch the substrate, etch a film deposited onto the substrate, and deposit metal or dielectric films onto the substrate. Because multiple chambers can process substrates concurrently, the throughput of cluster machines can be high.
However, typically, the deposition chambers within cluster machines are configured to deposit only one metal or dielectric film. Consequently, in a process requiring multiple layers of metals or dielectric films to be deposited on a substrate, the cluster machine deposits multiple layers sequentially in different process chambers. Thus, conventional cluster tools have a limited capability to deposit multiple layer film coatings, without having to reconfigure the process chambers. Due to the transport of the substrates between the multiple chambers, cluster machines can suffer from positional errors of the type discussed above.
Another conventional processing machine employs batch processing. Batch processing machines process a plurality of substrates (i.e., a batch) concurrently. Typically, such machines load substrates into a process chamber either one-by-one or by first loading the substrates onto a pallet or a tray and then loading the pallet into the process chamber. Batch processing machines can provide a high output, but are typically difficult to automate, difficult to scale to large wafer sizes and/or suffer from substrate alignment errors of the type discussed above.
Another conventional processing machine employs inline processing. Inline processing machines process substrates one by one, though a series of process steps. While, inline processing machines are versatile and have relatively high throughput, one disadvantage is that that the throughput is limited by the process time of the longest process step. Another disadvantage of the inline machines is that due to the use of separate stations for loading and unloading the substrates, they are structurally relatively long as compared to other processing machines. Thus, inline machines may be difficult to locate in space constrained processing facilities.
Thus, there exists a need for a relatively inexpensive, noncomplex mechanism for reducing accumulation of positioning errors. There also exists a need for a substrate processing approach that better lends itself to automation, has improved throughput, and more easily scales for varying wafer sizes.
The invention generally relates to pallets adapted for holding substrates during processing and to substrate processing machines adapted to employ the substrate processing pallets. According to one embodiment, a substrate processing pallet according to the invention provides features for maintaining improved substrate alignment during processing. According to further embodiments, the substrate processing pallet of the invention provides features for facilitating the loading of substrates onto the pallet; thus, simplifying the handling of substrate batches. According to a further feature, the processing pallet of the invention can accommodate substrates of varying sizes.
In one embodiment, a substrate processing pallet according to the invention has a top surface, a bottom surface and a plurality of side surfaces. The top surface has at least one recess adapted to receive a substrate. Each recess includes a support structure adapted to contact a portion of the substrate during processing. Each recess also includes a plurality of apertures. In one embodiment, during operation, a substrate processing machine initially extends lift pins through the apertures. A robot arm places a substrate onto the lift pins. The processing machine then retracts the lift pins to deposit the substrate onto the support structure of the recess. According to a further feature, each recess is chamfered to facilitate seating the substrate in the recess and on the support structure.
According to another feature, the substrate processing pallet includes a plurality of recesses and can accommodate a batch of substrates. According to a further embodiment, each recess has a particularly shaped outer edge portion adapted to interfit with a correspondingly shaped outer edge portion of a substrate to particularly align the substrate in the recess. According to an additional feature, each recess includes a protuberance adapted to interfit with a notch in a substrate to particularly align the substrate in the recess. In an alternative embodiment, each recess includes a flat outer edge portion adapted to interfit with a similarly flat outer edge portion of a substrate to particularly align the substrate in the recess.
According to another aspect of the invention, the recess has a bottom surface and the support structure includes a shoulder formed along a periphery of the recess and raised with respect to the bottom surface. In one embodiment, the shoulder maintains a gap between a bottom surface of the substrate and the bottom surface of the recess; thus, avoiding potentially damaging contact between the bottom surface of the recess and the bottom surface of the substrate, which may be populated with various devices. According to an additional feature, the shoulder also provides a path of thermal conductivity between the substrate and the substrate processing pallet. In a further embodiment, the alignment pin apertures are located in the support structure shoulder.
According to one embodiment, at least one of the side surfaces has a process positioning feature adapted to interfit and engage with a process chamber feature located inside of a process chamber to particularly position the pallet, and thus, the substrates on the pallet, within the process chamber. According to one embodiment, these features interoperate to effect lateral positioning. In another embodiment, the features engage to effect rotational positioning. According to a further feature, a first one of the side surfaces has a first transport positioning feature adapted to interfit and engage with a first end effector alignment feature of a first transport mechanism to particularly position the pallet, and thus, the substrates on the pallet, with respect to the first end effector. According to one embodiment, these features interoperate to effect rotational alignment. In another embodiment, the features interoperate to effect lateral alignment. According to another feature, the first side surface also has one or more first support features, each adapted to interfit and engage with a corresponding first end effector support feature of the first transport mechanism to support the pallet on the first end effector during transport.
According to another embodiment, a second one of the side surfaces has a second transport positioning feature adapted to interfit and engage with a second end effector alignment feature of a second transport mechanism to particularly position the pallet, and thus, the substrates on the pallet, with respect to the second end effector. According to one embodiment, these features interoperate to effect rotational alignment. In another embodiment, the features interoperate to effect lateral alignment. According to another feature, the second side surface also has one or more second support features, each adapted to interfit and engage with a corresponding second end effector support feature of the second transport mechanism to support the pallet on the second end effector during transport.
According to one embodiment, while the pallet is located in a load lock, a robot arm places substrates onto lift pins extending through apertures in each of the recesses. The lift pins then retract to seat each substrate on the support structure of each recess. The end effector of the first transport mechanism engages the substrate processing pallet via the first support and transport alignment features to transport the pallet from the load lock to a first process chamber. During such transport, the first end effector alignment feature slidingly interfits and engages with the first transport position feature to position the substrate processing pallet with respect to the first end effector. Also, the first end effector support features slidingly interfits and engages with the support features located in the first side surface.
A multistage elevator located below the first process chamber and including an elevator platform located inside of the first process chamber is adapted to receive the first transport mechanism. In one embodiment, the multistage elevator platform includes lower and upper elevator stages, wherein the upper stage is vertically aligned and separated from the lower stage. Each of the lower and upper elevator stages are adapted to support a substrate processing pallet and to accept the first transport mechanism. According to a further feature, each of the lower and upper elevator stages include at least one of the previously mentioned process chamber features adapted to engage with the process alignment feature or features located on one or more side surfaces of the substrate processing pallet.
In one embodiment, the first transport mechanism transports the substrate processing pallet between the load lock and the first process chamber. As the first transport mechanism transports the substrate processing pallet into the first process chamber, the multistage elevator raises the elevator platform to support the substrate processing pallet on the upper elevator stage. As the multistage elevator platform rises, one or more process chamber features located on the upper elevator stage rise to slidingly engage with corresponding process positioning features located on one or more side surfaces of the substrate processing pallet. According to one embodiment, the process positioning features on the side surfaces are chamfered notched apertures and the process chamber features are horizontally oriented, cylindrically shaped positioning pins, wherein a substantially cylindrically shaped side surface of each pin interfits and engages with each notched process position feature as the multistage elevator platform rises to support the substrate processing pallet. In a further embodiment, the first transport mechanism retracts subsequent to the multistage elevator platform assuming support of the substrate processing pallet.
According to a further embodiment, a second process chamber couples to the first process chamber, and the multistage elevator platform is further adapted to receive a second transport mechanism adapted to transport the substrate processing pallet between the first chamber and the second chamber. In one embodiment, the multistage elevator aligns the second side surface of the substrate processing pallet with a second end effector of the second transport mechanism. The second end effector then engages the substrate processing pallet via the second support and transport alignment features to transport the pallet from the first process chamber to the second process chamber.
During such transport, the second end effector alignment feature slidingly interfits and engages with the second transport position feature to position the substrate processing pallet with respect to the second end effector. Also, the second end effector support features slidingly interfits and engages with the support features located on the second side surface. As the second transport mechanism supports the substrate processing pallet on the second end effector, the multistage elevator lowers the elevator platform to disengage the process chamber features located on the upper elevator stage from the corresponding process positioning features located on one or more side surfaces of the substrate processing pallet.
According to one embodiment, the end effector alignment features are tapered to facilitate sliding engagement with chamfered, notched transport positioning features. In a further embodiment, each notched transport positioning feature is substantially centrally located along a longitudinal axis of the side surface on which it is located. In this way, thermal expansion and contraction of the substrate processing pallet tends to effect the position of the pallet with respect to the end effector symmetrically. According to another feature, the support features of the substrate processing pallet are sized and positioned such that thermal expansion and contraction of the substrate processing pallet causes substantially no mechanical stresses to occur between the pallet support features and the end effector support features with which the pallet support features interfit and engage.
In one embodiment, the substrate processing machine is adapted to concurrently transport a batch of substrates contained on a pallet while processing another batch of substrates contained on another pallet. According to a further embodiment, the substrate processing machine is adapted to perform repetitive cycles of such concurrent processing. In one such embodiment, the substrate processing machine begins in an initial state with a first substrate processing pallet in a load lock, a second processing pallet in a first process chamber and a third processing pallet in a second process chamber (with the first, second and third pallets not containing any substrates) and ends with removal of processed substrates from the load lock.
According to one embodiment, the first pallet is supported by the end effector of the first transport mechanism in the load lock, the second pallet is located in the upper stage of the elevator platform in the first processing chamber and the third pallet is supported by the end effector of the second transport mechanism inside of the second process chamber. According to a further aspect, a pin elevator raises a pin platform to extend the lift pins through lift pin apertures of the recesses of the first processing pallet. The robot arm then transfers substrates onto the lift pins of each recess of the first substrate processing pallet. The pin elevator then lowers the pin plate to retract the lift pins through the lift pin apertures of the first processing pallet; thus, lowering the substrates into the recesses of the first processing pallet.
According to another aspect, either prior to, subsequent to, or concurrently with loading substrates onto the first processing pallet, a multistage elevator aligns the lower stage of the elevator platform with the second end effector. The second transport then extends the second end effector to place the third pallet in vertical alignment with the lower stage of the elevator platform. Subsequent to such alignment, the elevator raises the elevator platform to bring the lower stage of the elevator platform into supporting contact with an underside of the third pallet, and to interfit and engage the process chamber alignment features located on the lower stage of the elevator platform with the process alignment features of the third pallet. According to a further embodiment, subsequent to the lower stage being brought into contact with the underside of the third pallet, the second transport retracts the second end effector back into the second process chamber.
According to a further feature, the second transport next extends into the first process chamber to remove the second pallet from the upper stage of the elevator platform. According to one embodiment, the elevator aligns the upper level of the elevator platform with the second end effector. The second transport then extends the second end effector to engage the second pallet with the support and alignment features of the second end effector. Once the second end effector is positioned to support the second pallet, the elevator raises the elevator platform to disengage the chamber features located on the upper stage of the elevator platform from the process alignment features located on the second substrate. Subsequent to disengagement, the second transport retracts the second end effector and thus, the second processing pallet into the second process chamber.
Next, according to a further embodiment, the first pallet transport extends the first end effector to transport the first pallet into the upper stage of the elevator platform. Subsequent to the first end effector vertically aligning the first pallet above the upper, the multistage elevator raises the elevator platform to bring the upper stage of the elevator platform into supporting contact with a bottom surface of the first pallet. Raising the elevator platform also causes the process chamber alignment features located on the upper stage of the elevator platform to interfit and engage with the process alignment features of the first pallet. Once the upper stage of the elevator platform assumes support of the first pallet, the first transport retracts to remove the first end effector from the first process chamber.
Next, according to a further embodiment, the first transport extends into the first process chamber to remove the third pallet from the lower stage of the elevator platform. According to one embodiment, the elevator aligns the lower level of the elevator platform with the first end effector. The first transport then extends the first end effector into the first process chamber to engage the third pallet with the support and alignment features of the first end effector. Once the first end effector is positioned to support the third pallet, the elevator raises the elevator platform to disengage the chamber alignment features located on the lower stage of the elevator platform from the process alignment features located on the third pallet. Subsequent to disengagement, the first transport retracts the first end effector and thus, the third pallet into the load lock.
With the first pallet now being the sole pallet inside of the first process chamber, the substrate processing machine, in one embodiment, cleans the batch of substrates contained on the first pallet. According to a further embodiment, concurrently with cleaning the substrates contained on the first pallet, the robot arm loads a batch of substrates onto the third pallet in the load lock according to the same process described above with respect to loading substrates onto the first pallet. Upon completion of the cleaning batch of substrates contained on the first pallet, the second transport transports the second pallet from the second process chamber into the lower stage of the elevator platform according to the same method described above for the transfer of the third pallet from the second process chamber to the first process chamber. Next, the second transport transports the first pallet, according to the same process described above with respect to the transport of the second pallet, from the upper stage of the elevator platform into the second process chamber. According to a further operational feature, the substrate processing machine then begins deposition processing the batch of substrates contained on the first pallet in the second process chamber.
According to a further feature of the invention, concurrently with the deposition processing of the substrate batch contained on the first pallet, the first transport transports the third pallet from the load lock to the upper stage of the elevator platform according to the same method described above for the transfer of the first pallet from the load lock into the first process chamber. Next, the first transport transports the second pallet from the lower stage of the elevator platform into the load lock according to the same method described above with respect to transferring the second pallet from the first process chamber into the load lock.
According to a further embodiment, concurrently with the deposition processing of the substrate batch contained on the first pallet, the substrate processing machine also cleans the batch of substrates contained on the third pallet in the first process chamber. In another aspect, concurrent with the deposition and cleaning, the robot arm loads a batch of substrates into the second pallet.
According to an additional embodiment, upon completion of the deposition processing in the second process chamber and the cleaning processing in the first process chamber, the second transport transports the first pallet into the lower stage of the elevator platform, according to the same method employed above to transfer the third pallet from the second process chamber to the first process chamber. Next, the second transport transports the third pallet from the upper stage of the elevator platform into the second process chamber according to the same method described above with respect to transporting the second pallet from the first process chamber into the second process chamber.
In one operational embodiment, concurrently with the substrate processing machine performing deposition processing in the second process chamber on the substrate batch contained on the third pallet, the first transport transports the second pallet from the load lock to the upper stage of the elevator platform according to the same method described above with respect to transporting the first pallet from the load lock into the first process chamber. Next, the first transport transports the first pallet from the lower stage of the elevator platform into the load lock according to the same method as described above for transporting the second pallet from the first process chamber into the load lock.
According to an additional processing aspect, concurrently, with the substrate processing machine deposition processing the substrate batch contained on the third pallet in the second process chamber and cleaning the substrate batch contained on the second pallet in the first process chamber, the robot arm removes the batch of processed substrates from the pallet to storage and reloads another batch of substrates onto the first pallet to begin the next processing cycle.
The above and further advantages of the invention may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in a which depicted element may not be drawn to scale, like elements are referenced with like reference designations and in which: